The Histology/Surgery Core provides the intellectual and physical environment in which Center Investigators, their trainees and support staff can learn and perform a variety of surgical and histological procedures. The Core will 1) Aims 1A, 2A: maintain existing shared facilities for animal surgery and histological processing, 2) Aims 1B, 2B: provide technical expertise and training in surgical techniques (both acute and chronic) and histological techniques for tissue processing of both peripheral and central auditory structures at the light- and electron-microscopic levels, 3) Aim 2D: continue to research improvements and refinements to histological and surgical methods, and 4) Aim 1E: assist with mouse husbandry in maintaining and propagating mutant lines. Some complex surgical techniques, such as preparation of the anesthetized cat for neurophysiological study, will be routinely offered as a technical service (Aims 1C, 1D). Some histological processing will be performed as a technical service, but only when task complexity and limited project scope make it inefficient to train the relevant group (Aim 2C). Facility maintenance will include 1) ordering of supplies, 2) preparation of stock solutions, 3) equipment repair, and 4) compliance with local and federal regulations. All research groups in the Center will benefit by the time saved in not duplicating these basic services. All investigators will also benefit from the repository of experience and expert advice the Core represents. First, significant time will be saved by offloading to Core personnel the task of training new students and new investigator-specific support staff. Second, Core expertise will enhance the research of all participants by 1) facilitating the incorporation of new techniques and 2) allowing them to use a wide range of techniques, each on a phasic basis, without having to maintain all the requisite skills within their own group. Core is staffed by one experienced individual with demonstrated expertise in all relevant areas, including animal surgery, immunohistpchemistry and a wide range of embedding and staining techniques for light- and electron-microscopic evaluation of peripheral and central auditory structures.